This invention relates generally to gas turbine engine turbines and more particularly to structural members of such engines.
Gas turbine engines frequently include a stationary turbine frame (also referred to as an inter-turbine frame or turbine center frame) which provides a structural load path from bearings which support the rotating shafts of the engine to an outer casing, which forms a backbone structure of the engine. Turbine frames commonly include an annular, centrally-located hub surrounded by an annular outer ring, which are interconnected by a plurality of radially-extending struts. The turbine frame crosses the combustion gas flowpath of the turbine and is thus exposed to high temperatures in operation. Such frames are often referred to as “hot frames”, in contrast to other structural members which are not exposed to the combustion gas flowpath.
To protect them from high temperatures, turbine frames are typically lined with high temperature resistant materials that isolate the frame structure from hot flow path gasses. The liner must provide total flow path coverage including the frame outer ring or case, hub structure and struts.
To protect the struts, a one-piece wraparound fairing is most common. This configuration requires the struts be separable from the frame assembly at the hub, outer ring or both to permit fairing installation over the struts. This makes installation and field maintenance difficult.
A transversely-split 360° combined fairing/nozzle arrangement is also known. This arrangement splits the fairing/nozzle assembly into forward and aft 360° ring sections allowing assembly to a one-piece frame by sandwiching the frame between forward and aft ring sections and bolting the sections together. This configuration is only suitable for passively cooled nozzle cascades.
Another known configuration is an interlocking split fairing arrangement in which forward and aft sections of individual fairing/nozzle components are sandwiched around the struts. This arrangement relies on a interlocking feature to keep the fairing halves together after assembly to the frame. This interlocking feature consumes a significant amount of physical space and is therefore not suitable for use with many frame configurations.